Communication relay device for train and communication relay method for train

ABSTRACT

When data is transmitted from a first communication terminal to a second communication terminal, a communication relay device converts car identification information of a communication source of communication-source identification information included in a communication packet into a car number of a vehicle, and transmits the data to an inter-vehicle communication path. When data is transmitted from the second communication terminal to the first communication terminal, the communication relay device converts car identification information of a communication destination of communication-destination identification information included in a communication packet into a “0”-th car indicating own car, and transmits the data to an in-vehicle communication path.

TECHNICAL FIELD

The present invention relates to a communication relay device for a train and a communication relay method thereof.

BACKGROUND ART

Conventionally, TCP/IP has been well known as a communication protocol. In TCP/IP, an IP address is used as information to identify each device when communications between devices are performed. That is, when TCP/IP is used, uniquely determined IP addresses are allocated to devices on a network.

When each device transmits communication data to a network, the device transmits the data, attaching a transmission-destination IP address and a transmission-source IP address to the data. When communications are performed using plural networks, a communication relay device connecting the networks performs a path control using a transmission-destination IP address, and transfers communication data to a device that has the transmission-destination IP address.

When a local network is connected to the Internet, an IP address attached to communication data of a device on the local network is converted by a method called Network Address Translation (NAT). A NAT processing unit that performs NAT holds an IP address on the Internet, converts a transmission-source IP address, which is attached to communication data transmitted by a device on a local network and is received by the NAT processing unit, into an IP address on the Internet held by the NAT processing unit, and transmits after conversion the communication data to the Internet. The NAT processing unit also holds an IP address on a local network, converts a transmission-destination IP address, which is attached to communication data received from the Internet, into an IP address of a device on the local network, and transmits after conversion the communication data to the local network. In this way, a device on the local network can communicate with a device on the Internet via the NAT processing unit.

A technique of NAT can be used not only for communications between a local network and the Internet but also for communications between plural local networks having different network addresses (for example, see Nonpatent Literature 1).

Conventionally, to perform communications between devices arranged in vehicles of a train, there has been known a technique of performing communications via a communication relay device by arranging the communication relay device in each vehicle. For example, Patent Document 1 discloses a communication relay device that rewrites relative vehicle-formation numbers of a destination address and a transmission source address of a data communication packet. With this configuration, communications between arbitrary communication terminals installed in vehicles can be continued even when vehicle formations are merged.

-   Patent Document 1: Japanese Patent Application Laid-open No.     2004-201476 -   Nonpatent Literature 1: ‘Internetworking with TCP/IP’, by Douglas E.     Comer, Vol. 1, 4th Edition, August 2002, KYORITSU SHUPPAN Co., Ltd.

DISCLOSURE OF INVENTION Problem to be Solved by the Invention

Consider a situation where TCP/IP is used as a communication protocol for communications between devices installed in vehicles of a train, which has a vehicle formation of plural vehicles. Trains are made up of individually manufactured vehicles. Thus, it is desirable that the same type of devices installed in respective vehicles have the same IP address, from a viewpoint of manufacturing, management, and maintenance of vehicles.

An operation method of using the same IP address for devices in each formation can be considered if vehicles in each formation are not changed around. However, because trains are used such that formations thereof are merged and divided, communications cannot be performed normally when there are devices that have the same IP address at the time of merging. Thus, a method of allocating IP addresses to the all formations that have a possibility to be connected is considered. However, this has a problem in that mergeable and dividable formations are limited by size limitation of an IP address space, and management of an IP address for each device becomes complex.

Consider a situation where network addresses for respective formations are determined and TCP/IP is used. When an operation is performed such that two networks can physically communicate with each other at the time of formation merging, communications using TCP/IP become possible by providing NAT between the two networks. However, two network addresses to be merged need to be different from each other. Although a method of allocating network addresses to the all formations that have a possibility to be merged is considered, this has a problem in that mergeable and dividable formations are limited by size limitation of a network address space, and management of a network address for each formation becomes complex.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a communication relay device for a train and a communication relay method thereof making it possible to perform communications between devices and facilitate management of communication identification information even when communication identification information such as a redundant IP address is given to the same type of devices installed in different vehicles, and making it possible to perform a flexible operation at the time of merging or dividing vehicle formations.

Means for Solving Problem

To solve the problems described above and achieve the object, a communication relay device for a train according to the present invention, which is mounted on a vehicle of a train having a vehicle formation including a plurality of vehicles, connected to an inter-vehicle communication path and to an in-vehicle communication path, and capable of relaying communications between communication terminals installed within own vehicle and communications between communication terminals installed in different vehicles, includes: an inter-vehicle communication interface capable of transmitting and receiving a communication packet via the inter-vehicle communication path; an in-vehicle communication interface capable of transmitting and receiving a communication packet via the in-vehicle communication path; and an identification-information converting unit that sets, when vehicle identification information of a communication destination included in communication-destination identification information of a communication packet received from the in-vehicle communication path via the in-vehicle communication interface indicates other vehicle, vehicle identification information for identifying a position of own vehicle within the vehicle formation as vehicle identification information of a communication source included in communication-source identification information of the communication packet and then transmits the communication packet to the inter-vehicle communication path via the inter-vehicle communication interface, and sets, when vehicle identification information of a communication destination included in communication-destination identification information of a communication packet received from the inter-vehicle communication path via the inter-vehicle communication interface indicates own vehicle, vehicle identification information indicating own vehicle and used in common by each vehicle within the vehicle formation as the vehicle identification information of the communication destination and then transmits the communication packet to the in-vehicle communication path via the in-vehicle communication interface.

Effect of the Invention

According to the present invention, in communications between communication terminals installed in different vehicles within a vehicle formation, vehicle identification information for identifying a position of a vehicle within a formation is attached to communication-destination identification information and communication-source identification information. Thus, a communication destination can be identified and communications can be performed even when the same identification information is used for the same type of communication terminals in each vehicle. Therefore, it is not necessary to set to communication terminals identification information different for each vehicle, and train operations can be performed flexibly.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram that includes a configuration of a communication relay device for a train according to a first embodiment of the present invention.

FIG. 2 is an arrangement diagram of communication relay devices in FIG. 1 within a vehicle formation.

FIG. 3 depicts a structure of a communication packet transmitted and received by communication terminals according to the first embodiment.

FIG. 4 depicts a structure of a communication packet in the first embodiment when a communication terminal of a first car transmits data to a communication terminal of a second car.

FIG. 5 depicts a structure of a communication packet in the first embodiment transmitted from a communication relay device in the first car to an inter-vehicle communication path.

FIG. 6 depicts a structure of a communication packet in the first embodiment received by the communication terminal of the second car.

FIG. 7 is an arrangement diagram of communication relay devices for a train within a train according to a second embodiment of the present invention.

FIG. 8 depicts a structure of a communication packet transmitted and received by communication terminals according to the second embodiment.

FIG. 9 depicts a structure of a communication packet in the second embodiment transmitted from a communication terminal of a first car of a first to a communication terminal of a first car of a second formation.

FIG. 10 depicts a structure of a communication packet in the second embodiment transmitted from a communication relay device in the first car of the first formation to an inter-vehicle communication path.

FIG. 11 depicts a structure of a communication packet in the second embodiment received by the communication terminal of the first car of the second formation.

FIG. 12 is an arrangement diagram of communication relay devices for a train within a formation according to a third embodiment of the present invention.

FIG. 13 depicts a structure of a communication packet transmitted and received by communication terminals of the third embodiment.

FIG. 14 is an arrangement diagram of communication relay devices for a train within a formation according to a fourth embodiment of the present invention.

FIG. 15 is an arrangement diagram of communication relay devices for a train within a formation according to a fifth embodiment of the present invention.

FIG. 16 is an arrangement diagram of a communication relay device for a train within a formation according to a sixth embodiment of the present invention.

FIG. 17 depicts a structure of a communication packet transmitted and received by communication terminals of the sixth embodiment.

FIG. 18 is an example of a structure of a communication packet in the sixth embodiment transmitted from a communication terminal 51 a.

FIG. 19 is an example of a structure of a communication packet in the sixth embodiment transmitted from a communication terminal 51 b.

FIG. 20 is an example of a structure of a communication packet in the sixth embodiment transmitted by the communication terminal 51 a to the communication terminal 51 b.

FIG. 21 is an example of a structure of a communication packet in the sixth embodiment received by the communication terminal 51 b.

FIG. 22 is an example of a structure of a communication packet in the sixth embodiment transmitted by the communication terminal 51 b to the communication terminal 51 a.

FIG. 23 is an example of a structure of a communication packet in the sixth embodiment received by the communication terminal 51 a.

EXPLANATIONS OF LETTERS OR NUMERALS

-   -   1, 16 a, 16 b, 16 c, 16 d Communication relay device     -   2, 15 Inter-vehicle communication path     -   3, 17 a, 17 b, 17 c, 17 d In-vehicle communication path     -   4, 5, 18 a, 18 b, 18 c, 18 d Communication terminal     -   6 Identification-information converting unit     -   7 Inter-vehicle communication interface     -   8 In-vehicle communication interface     -   9, 10, 11 Vehicle     -   12, 13 Formation     -   14 a, 14 b Vehicle     -   55 Format-information storage unit     -   56 Format determining unit

BEST MODE(S) FOR CARRYING OUT THE INVENTION

Exemplary embodiments of a communication relay device for a train and a communication relay method for a train according to the present invention will be explained below in detail with reference to the accompanying drawings. The present invention is not limited to the embodiments.

First Embodiment

FIG. 1 is a block diagram that includes a configuration of a communication relay device for a train according to a first embodiment of the present invention. In FIG. 1, a communication relay device 1 is a communication relay device for a train installed within a vehicle, and the communication relay device 1 is connected to an inter-vehicle communication path 2 and is also connected to an in-vehicle communication path 3. For example, communication terminals 4 and 5 are connected to the in-vehicle communication path 3. The inter-vehicle communication path 2 is a communication path to connect vehicles. The in-vehicle communication path 3 is a communication path installed within each vehicle, and connects the communication terminals 4 and 5 within a vehicle and the communication relay device 1. The communication terminals 4 and 5 are examples of various devices capable of transmitting and receiving data installed within a vehicle, and the number of these communication terminals is not limited to two and can be any arbitrary number.

The communication relay device 1 includes an identification-information converting unit 6, an inter-vehicle communication interface 7 connected to the identification-information converting unit 6 and the inter-vehicle communication path 2, and an in-vehicle communication interface 8 connected to the identification-information converting unit 6 and the in-vehicle communication path 3. Communications between the communication terminal 4 and the communication terminal 5 are performed using the in-vehicle communication path 3. When the communication terminal 4 or 5 communicates with a communication terminal installed in other vehicle, the communication terminal 4 or 5 performs communications using the inter-vehicle communication path 2 via the communication relay device 1. The identification-information converting unit 6 is explained below with reference to FIG. 2.

FIG. 2 is an arrangement diagram of communication relay devices in FIG. 1 within a vehicle formation. In FIG. 2, vehicles 9, 10, and 11, as three vehicles, are connected in this order to form a vehicle formation (hereinafter, “formation”), for example. Assume that the vehicle 9 is a first car, the vehicle 10 is a second car, and the vehicle 11 is a third car, for the formation.

In the vehicle 9, a communication relay device 1 a and communication terminals 4 a and 5 a are installed, and these are connected by an in-vehicle communication path 3 a. The communication relay device 1 a has a configuration identical to that of the communication relay device 1 in FIG. 1. Therefore, although not shown, the communication relay device 1 a includes an identification-information converting unit 6 a, an inter-vehicle communication interface 7 a, and an in-vehicle communication interface 8 a. A connection mode of the communication relay device 1 a, the communication terminals 4 a and 5 a, and the in-vehicle communication path 3 a is also identical to that of the communication relay device 1, the communication terminals 4 and 5, and the in-vehicle communication path 3 in FIG. 1. The communication terminals 4 a and 5 a are also devices having a communication function capable of transmitting and receiving data.

Similarly, in the vehicle 10, a communication relay device 1 b and communication terminals 4 b and 5 b are installed, and these are connected by an in-vehicle communication path 3 b. Although not shown, the communication relay device 1 b includes an identification-information converting unit 6 b, an inter-vehicle communication interface 7 b, and an in-vehicle communication interface 8 b. In the vehicle 11, a communication relay device 1 c and communication terminals 4 c and 5 c are installed, and these are connected by an in-vehicle communication path 3 c. Similarly, although not shown, the communication relay device 1 c includes an identification-information converting unit 6 c, an inter-vehicle communication interface 7 c, and an in-vehicle communication interface 8 c.

The communication relay device 1 a in the vehicle 9, the communication relay device 1 b in the vehicle 10, and the communication relay device 1 c in the vehicle 11 are connected to each other by an inter-vehicle communication path 2 a arranged between the vehicles 9, 10, and 11.

FIG. 3 depicts a structure of a communication packet transmitted and received by communication terminals according to the present embodiment. As shown in FIG. 3, the communication packet includes communication-destination identification information, communication-source identification information, and a data portion. The communication-destination identification information includes car identification information corresponding to a car number of a communication destination, and device identification information for identifying a communication terminal within a vehicle of the communication destination. The communication-source identification information includes car identification information corresponding to a car number of a communication source, and device identification information for identifying a communication terminal within a vehicle of the communication source.

The car identification information of a communication destination and that of a communication source destination are explained. For example, in the case of transmitting data from a communication terminal within the first car to a communication terminal within the second car, car identification information of a communication destination included in a communication packet transmitted by the communication terminal within the first car is car identification information indicating the second car (for example, a car number “2”). That is, car identification information of a communication destination is vehicle information for identifying a position of a vehicle within a formation. On the other hand, for car identification information of a communication source, specific car identification information indicating own vehicle (a specific value indicating own vehicle, such as “0” by indicating the own vehicle as the 0-th car) can be used, instead of using car identification information indicating the first car (for example, a car number “1”). That is, at the stage of transmitting a communication packet from a communication terminal of the first car, for own vehicle as a transmission source, specific car identification information indicating the own vehicle is used, instead of using a car number uniquely allocated within a formation. Accordingly, for vehicles other than the first car, when these vehicles indicate own vehicles, the specific car identification information indicating own vehicle can be commonly used. For example, in the case of transmitting and receiving data using the in-vehicle communication path 3 between communication terminals within the same vehicle, specific car identification information indicating the own vehicle is used for both the car identification information of a communication destination and that of a communication source.

The same device identification information (the same value) can be set to the communication terminals 4 a, 4 b, and 4 c, by regarding these communication terminals as the same type of devices. Similarly, the same device identification information (the same value) can be set to the communication terminals 5 a, 5 b, and 5 c, by regarding these, communication terminals as the same type of devices.

An operation in the present embodiment is explained next. A transmission of data from the communication terminal 4 a in the vehicle 9 as the first car to the communication terminal 4 b in the vehicle 10 as the second car is explained, as an example. A communication packet when the communication terminal 4 a installed in the first car transmits data to the communication terminal 4 b installed in the second car has a structure shown in FIG. 4.

As shown in FIG. 4, communication-destination identification information of the communication packet transmitted from the communication terminal 4 a includes car identification information indicating the second car (car identification information of the second car), and communication-terminal identification information indicating the communication terminal 4 b (device identification information of the communication terminal 4 b).

Communication-source identification information of the communication packet includes specific car identification information indicating own vehicle (car identification information of the own car), and communication-terminal identification information indicating the communication terminal 4 a (device identification information of the communication terminal 4 a). The specific car identification information indicating own vehicle (car identification information of the own car) is the “0”-th car indicating the own vehicle. The communication terminal 4 a transmits the communication packet to the in-vehicle communication path 3 a.

The communication relay device 1 a in the first car receives the communication packet from the in-vehicle communication path 3 a using the in-vehicle communication interface 8 a of the communication relay device 1 a itself. When finding a car identification number indicating other than the own vehicle in the communication-destination identification information of the communication packet received, the identification-information converting unit 6 a in the communication relay device 1 a stores the car identification number indicating the first car (the car identification information of the first car) into the car identification information of the communication-source identification information of the communication packet received. The communication relay device 1 a transmits a communication packet in which communication-source identification information is converted, to the inter-vehicle communication path 2 a using the inter-vehicle communication interface 7 a. FIG. 5 depicts a structure of a communication packet transmitted from the communication relay device 1 a to the inter-vehicle communication path 2 a.

The communication relay device 1 b in the second car receives the communication packet from the inter-vehicle communication path 2 a using the inter-vehicle communication interface 7 b of the communication relay device 1 b itself. When finding a car identification number of the second car as the own vehicle in the communication-destination identification information of the communication packet received, the identification-information converting unit 6 b in the communication relay device 1 b stores the specific car identification information indicating the own vehicle (the car number of the own car) into the car identification information of the communication-destination identification information of the communication packet received. The communication relay device 1 b transmits a communication packet in which communication-destination identification information is converted, to the in-vehicle communication path 3 b using the in-vehicle communication interface 8 b. FIG. 6 depicts a structure of a communication packet transmitted from the communication relay device 1 b to the in-vehicle communication path 3 b. This structure is also a structure of a communication packet received by the communication terminal 4 b.

The communication terminal 4 b in the second car receives the communication packet that includes device identification of a communication destination indicating the communication terminal 4 b itself from the in-vehicle communication path 3 b. In this case, the communication packet received by the communication terminal 4 b has a structure shown in FIG. 6. Therefore, the communication terminal 4 b can understand that the communication terminal 4 a installed in the first car is the transmission source.

The above-mentioned communications can be performed in a situation where path information is not present, because each of the communication relay devices 1 a to 1 c has a unit (not shown) that obtains car number information. That is, because the identification-information converting units 6 a, 6 b, and 6 c convert car identification information based on car number information of a car in which the converting unit itself is installed, the identification-information converting units 6 a, 6 b, and 6 c need to obtain the car number information. This can be dealt with through a method of obtaining car number information in which the communication relay devices 1 a to 1 c individually record car number information when a formation is formed.

In the present embodiment, communication-destination identification information and communication-source identification information can be IP addresses. An example of this method is explained.

An IP address can be expressed by an integer of four bytes, for example. For example, the first and second bytes are fixed values, the third byte is a car number, and the fourth byte is an integer (a terminal number) to identify a communication terminal. For a value of car identification information of own car, zero (0) is used, for example. A communication relay device installed in each vehicle has each car number set as car number information, at the time of formation manufacturing.

By performing the above setting, communication terminals can be individually identified even when IP addresses are determined by allocating the same terminal number to the same type of communication terminals in each car, and communications can be performed between vehicles. That is, it is possible to provide a system of communications on a network that uses device identification information such as redundant IP addresses for the same type of devices installed in different vehicles within a formation. Consequently, a communication terminal is not required to be set with device identification information different for each vehicle, and flexible train operations can be handled.

In the present embodiment, although an example of installing one communication relay device in each vehicle is explained, two or more communication relay devices can be installed within one vehicle.

A communication relay device simultaneously managing two or more vehicles can be installed. In this case, identification information is set such that a communication relay device identifies a range of communication terminals communicating by using an in-vehicle communication interface.

Second Embodiment

FIG. 7 is an arrangement diagram of communication relay devices for a train within a train according to a second embodiment of the present invention. In FIG. 7, the train includes two formations of a formation 12 and a formation 13, for example. The formation 12 is a first formation, and includes a vehicle 14 a and a vehicle 14 b, for example. The vehicle 14 a is a first car of the first formation, and the vehicle 14 b is a second car of the first formation. The formation 13 is a second formation, and includes a vehicle 14 c and a vehicle 14 d, for example. The vehicle 14 c is the first car of the second formation, and the vehicle 14 d is the second car of the second formation. The number of formations and the number of vehicles in each formation are examples, and these numbers are not limited thereto.

A communication relay device 16 a is installed in the vehicle 14 a, a communication relay device 16 b is installed in the vehicle 14 b, a communication relay device 16 c is installed in the vehicle 14 c, and a communication relay device 16 d is installed in the vehicle 14 d. An inter-vehicle communication path 15 is a communication path connecting vehicles. The communication relay devices 16 a, 16 b, 16 c, and 16 d are connected to the inter-vehicle communication path 15, and can communicate with each other using the inter-vehicle communication path 15. The inter-vehicle communication path 15 also works as an inter-formation communication path between the first formation and the second formation, that is, between the vehicle 14 b and the vehicle 14 c.

A communication terminal 18 a is installed in the vehicle 14 a, and the communication terminal 18 a is connected to the communication relay device 16 a via an in-vehicle communication path 17 a. Similarly, a communication terminal 18 b is installed in the vehicle 14 b, and the communication terminal 18 b is connected to the communication relay device 16 b via an in-vehicle communication path 17 b. Similarly, a communication terminal 18 c is installed in the vehicle 14 c, and the communication terminal 18 c is connected to the communication relay device 16 c via an in-vehicle communication path 17 c. Similarly, a communication terminal 18 d is installed in the vehicle 14 d, and the communication terminal 18 d is connected to the communication relay device 16 d via an in-vehicle communication path 17 d. The number of communication terminals installed in each vehicle is an example, and plural communication terminals can be connected as shown in FIG. 2.

The configuration of each of the communication relay devices 16 a, 16 b, 16 c, and 16 d is identical to the configuration of the communication relay device 1 according to the first embodiment. That is, each communication relay device includes an inter-vehicle communication interface, an identification-information converting unit, and an in-vehicle communication interface.

FIG. 8 depicts a structure of a communication packet transmitted and received by communication terminals according to the present embodiment. As shown in FIG. 8, the communication packet includes communication-destination identification information, communication-source identification information, and a data portion. The communication-destination identification information includes formation identification information corresponding to the formation number of a communication destination, and device identification information for identifying a communication terminal within a formation of the communication destination. The communication-source identification information includes formation identification information corresponding to the formation number of a communication source, and device identification information for identifying a communication terminal within a formation of the communication source.

When communication terminals performing communications are both within the same formation, specific identification information indicating own formation (for example, a value of a 0 (zero) formation as the own formation) is set as the formation identification information. This corresponds to the case of using specific car identification information indicating own vehicle for car identification information when communication terminals perform communications using the in-vehicle communication path 3 according to the first embodiment. For example, when the communication terminal 18 a transmits a communication packet to the communication terminal 18 b, in the communication packet, information corresponding to the own formation is used for the formation identification information of a communication destination, information corresponding to the communication terminal 18 b is used for the device identification information of a communication destination, information corresponding to the own formation is used for the formation identification information of a communication source, and information corresponding to the communication terminal 18 a is used for the device identification information of a communication source.

When communication terminals performing communications are within mutually different formations, information indicating a formation of a transmission destination is set as the formation identification information of a communication destination, and information indicating own formation is set as the formation identification information of a communication source. For example, when the communication terminal 18 a transmits a communication packet to the communication terminal 18 c, in the communication packet, information corresponding to the second formation is used as the formation identification information of a communication destination, information corresponding to the communication terminal 18 c is used for the device identification information of a communication destination, information corresponding to the own formation is used for the formation identification information of a communication source, and information corresponding to the communication terminal 18 a is used for the device identification information of a communication source. FIG. 9 depicts a structure of the communication packet. An operation of the present embodiment is explained below by exemplifying a case of transmitting a communication packet from the communication terminal 18 a to the communication terminal 18 c.

The communication relay device 16 a in the first car of the first formation receives the communication packet from the in-vehicle communication path 17 a using the in-vehicle communication interface of the communication relay device 16 a itself. When finding formation identification information indicating other than the own formation in the communication-destination identification information of the communication packet received, the identification-information converting unit in the communication relay device 16 a converts the formation identification information of the communication-source identification information of the communication packet received into formation identification information indicating the first formation (formation identification information of the first formation). The communication relay device 16 a transmits the communication packet, in which the communication-source identification information is converted, to the inter-vehicle communication path 15 using the inter-vehicle communication interface of the communication relay device 16 a itself. FIG. 10 depicts a structure of the communication packet in this case.

The communication relay device 16 c in the first car of the second formation receives the communication packet from the inter-vehicle communication path 15 using the inter-vehicle communication interface of the communication relay device 16 c itself. When finding formation identification information of the second formation as the own formation in the communication-destination identification information of the communication packet received, the identification-information converting unit in the communication relay device 16 c converts the formation identification information of the communication-destination identification information of the communication packet received into specific formation identification information indicating the own formation (formation identification information of the own formation). The communication relay device 16 c transmits the communication packet, in which the communication-destination identification information is converted, to the in-vehicle communication path 17 c using the in-vehicle communication interface of the communication relay device 16 c itself. FIG. 11 depicts a structure of the communication packet in this case.

The communication terminal 18 c in the first car of the second formation receives the communication packet that includes device identification information of a communication destination indicating the communication terminal 18 c from the in-vehicle communication path 17 c. In this case, the communication packet received by the communication terminal 18 c has the structure shown in FIG. 11. Therefore, the communication terminal 18 c can understand that the transmission source of the received communication packet is the communication terminal 18 a installed in the first formation.

The above-mentioned communications can be performed in a situation where path information is not present, because each of the communication relay devices 16 a to 16 f has a unit (not shown) that obtains formation information. That is, because each formation-information converting unit in the communication relay devices 16 a to 16 d converts formation identification information based on formation information of a car in which the converting unit itself is installed, the identification-information converting unit needs to obtain the formation information.

In the present embodiment, communication-destination identification information and communication-source identification information can be IP addresses, in a similar manner to that of the first embodiment.

According to the present embodiment, communications can be performed even when redundant device-identification information is used in the same type of devices installed in vehicles of different formations within a train. Consequently, a communication system can be easily constructed at the time of merging or dividing formations, flexible train operations can be handled.

Third Embodiment

FIG. 12 is an arrangement diagram of communication relay devices for a train within a train according to a third embodiment of the present invention. In FIG. 12, the train includes two formations of a formation 19 and a formation 20, for example. The formation 19 is a first formation, and includes a vehicle 22 a and a vehicle 22 b, for example. The vehicle 22 a is a first car of the first formation, and the vehicle 22 b is a second car of the first formation. The formation 20 is a second formation, and includes a vehicle 22 c and a vehicle 22 d, for example. The vehicle 22 c is the first car of the second formation, and the vehicle 22 d is the second car of the second formation. The number of formations and the number of vehicles in each formation are examples, and these numbers are not limited thereto.

A first communication relay device 23 a, a second communication relay device 24 a connected to the first communication relay device 23 a, a communication terminal 26 a, and an in-vehicle communication path 25 a connecting the second communication relay device 24 a and the communication terminal 26 a are installed in the vehicle 22 a. Similarly, a first communication relay device 23 b, a second communication relay device 24 b, a communication terminal 26 b, and an in-vehicle communication path 25 b are installed in the vehicle 22 b. A first communication relay device 23 c, a second communication relay device 24 c, a communication terminal 26 c, and an in-vehicle communication path 25 c are installed in the vehicle 22 c. A first communication relay device 23 d, a second communication relay device 24 d, a communication terminal 26 d, and an in-vehicle communication path 25 d are installed in the vehicle 22 d. The number of communication terminals installed in each vehicle is an example, and plural communication terminals can be connected as shown in FIG. 2.

An inter-vehicle communication path 21 is a communication path connecting vehicles. The first communication relay devices 23 a, 23 b, 23 c, and 23 d are connected to the inter-vehicle communication path 21, and can communicate with each other using the inter-vehicle communication path 21. The inter-vehicle communication path 21 also works as an inter-formation communication path between the first formation and the second formation, that is, between the vehicle 22 b and the vehicle 23 c.

FIG. 13 depicts a structure of a communication packet transmitted and received by communication terminals of the present embodiment. As shown in FIG. 13, the communication packet includes communication-destination identification information, communication-source identification information, and a data portion. The communication-destination identification information includes formation identification information corresponding to the formation number of a communication destination, car identification information corresponding to a car number of the communication destination, and device identification information for identifying a communication terminal within a vehicle of the communication destination. The communication-source identification information includes formation identification information corresponding to the formation number of a communication source, car identification information corresponding to a car number of the communication source, and device identification information for identifying a communication terminal within a vehicle of the communication source.

Each of the first communication relay devices 23 a, 23 b, 23 c, and 23 d has an identification-information converting unit that converts formation identification information. Each of the first communication relay devices 23 a, 23 b, 23 c, and 23 d also has an inter-vehicle communication interface. Each of the second communication relay devices 24 a, 24 b, 24 c, and 24 d has an identification-information converting unit that converts car identification information. Each of the second communication relay devices 24 a, 24 b, 24 c, and 24 d also has an in-vehicle communication interface.

Each of the first communication relay devices 23 a, 23 b, 23 c, and 23 d converts the formation identification information explained in the second embodiment, and each of the second communication relay devices 24 a, 24 b, 24 c, and 24 d converts the car identification information explained in the first embodiment. By converting the car identification information, each communication terminal can communicate using unique identification information within the formation even when identification information of a communication terminal installed in each vehicle is used in other car and when a formation is constructed by combining vehicles. Each communication terminal can communicate using unique identification information even when plural formations are combined and connected to operate as a train. That is, even when the same device identification information is used in communication terminals of the same device between vehicles within a formation or between formations, each communication terminal can communicate using unique identification information by attaching formation identification information and car identification information to a communication packet and by properly converting these pieces of information. In the present embodiment, a car installed with each communication terminal can be assigned by plural (two, in this case) pieces of identification information at the time of assigning each communication terminal to perform communications, in a similar manner to that of the first embodiment. That is, cars can be assigned using an expression of a specific car identification number indicating own vehicle or a car number within a formation of the own vehicle to each communication terminal, and a communication relay device converts these pieces of identification information. This also applies to formation identification information, and each communication terminal can be accessed by plural methods in this way. Other configurations, operations, and effects of the third embodiment are identical to those of the first and second embodiments.

Fourth Embodiment

FIG. 14 is an arrangement diagram of communication relay devices for a train within a train according to a fourth embodiment of the present invention. In FIG. 14, the train includes two formations of a formation 27 and a formation 28, for example. The formation 27 is a first formation, and includes a vehicle 30 a and a vehicle 30 b, for example. The vehicle 30 a is a first vehicle (a first car) in the first formation, and the vehicle 30 b is a second vehicle (a second car) in the first formation. The formation 28 is a second formation, and includes a vehicle 30 c and a vehicle 30 d, for example. The vehicle 30 c is a first vehicle (the first car) in the second formation, and the vehicle 30 d is a second vehicle (the second car) in the second formation. The number of formations and the number of vehicles in each formation are examples, and these numbers are not limited thereto.

A communication relay device 31 a, a communication terminal 33 a, and an in-vehicle communication path 32 a connecting the communication relay device 31 a and the communication terminal 33 a are installed in the vehicle 30 a. A communication relay device 31 b, a communication terminal 33 b, and an in-vehicle communication path 32 b connecting the communication relay device 31 b and the communication terminal 33 b are installed in the vehicle 30 b. A communication relay device 31 c, a communication terminal 33 c, and an in-vehicle communication path 32 c connecting the communication relay device 31 c and the communication terminal 33 c are installed in the vehicle 30 c. A communication relay device 31 d, a communication terminal 33 d, and an in-vehicle communication path 32 d connecting the communication relay device 31 d and the communication terminal 33 d are installed in the vehicle 30 d. The number of communication terminals installed in each vehicle is an example, and plural communication terminals can be connected as shown in FIG. 2.

An inter-vehicle communication path 29 is a communication path connecting vehicles. The communication relay devices 31 a, 31 b, 31 c, and 31 d are connected to the inter-vehicle communication path 29, and can communicate with each other using the inter-vehicle communication path 29. The inter-vehicle communication path 29 also works as an inter-formation communication path between the first formation and the second formation, that is, between the vehicle 30 b and the vehicle 30 c.

The communication relay device 31 a includes an inter-vehicle communication interface 34 a, a first identification-information converting unit 35 a, a second identification-information converting unit 36 a, and an in-vehicle communication interface 37 a. Similarly, the communication relay device 31 b includes an inter-vehicle communication interface 34 b, a first identification-information converting unit 35 b, a second identification-information converting unit 36 b, and an in-vehicle communication interface 37 b. The communication relay device 31 c includes an inter-vehicle communication interface 34 c, a first identification-information converting unit 35 c, a second identification-information converting unit 36 c, and an in-vehicle communication interface 37 c. The communication relay device 31 d includes an inter-vehicle communication interface 34 d, a first identification-information converting unit 35 d, a second identification-information converting unit 36 d, and an in-vehicle communication interface 37 d.

Each of the first identification-information converting units 35 a, 35 b, 35 c, and 35 d converts formation identification information, and performs an operation equivalent to that of the identification-information converting units of the first communication relay devices 23 a, 23 b, 23 c, and 23 d according to the third embodiment. Each of the second identification-information converting units 36 a, 36 b, 36 c, and 36 d converts car identification information, and performs an operation equivalent to that of the identification-information converting units of the second communication relay devices 24 a, 24 b, 24 c, and 24 d according to the third embodiment.

For example, a case that the communication terminal 33 a installed in the first vehicle 30 a in the first formation transmits data to the communication terminal 33 c installed in the first vehicle 30 c in the second formation is explained. Communication-destination identification information of a communication packet transmitted from the communication terminal 33 a includes formation identification information of the second formation as formation identification information of a communication destination, car identification information of the first car as car identification information of the communication destination, and device identification information of the communication terminal 33 c as device identification information of the communication destination. Communication-source identification information of a communication packet transmitted from the communication terminal 33 a includes formation identification information of the own formation as formation identification information of a communication source, car identification information of the own car as car identification information of the communication source, and device identification information of the communication terminal 33 a as device identification information of the communication source. A communication packet transmitted from the communication terminal 33 a passes through the in-vehicle communication path 32 a, and is received by the communication relay device 31 a via the in-vehicle communication interface 37 a. In the communication relay device 31 a, when the second identification-information converting unit 36 a finds formation identification information other than the own formation or finds car identification information other than the own car in the communication-destination identification information of the communication packet received, the second identification-information converting unit 36 a converts the car identification information of the communication source of the communication packet received, from the car identification information of the own car into the car identification information of the first car, and outputs the car identification information of the first car to the first identification-information converting unit 35 a. When the first identification-information converting unit 35 a finds formation identification information other than the own formation in the communication-destination identification information of the communication packet output from the second identification-information converting unit 36 a, the first identification-information converting unit 35 a converts the formation identification information of the communication source of the communication packet, from the formation identification information of the own formation into the formation identification information of the first formation, and transmits the communication packet to the inter-vehicle communication path 29 via the inter-vehicle communication interface 34 a. The communication relay device 31 c in the first vehicle 30 c in the second formation receives the communication packet from the inter-vehicle communication path 29 via the inter-vehicle communication interface 34 c. In the communication relay device 31 c, when the first identification-information converting unit 35 c finds identification information of the second formation as the own formation in the communication-destination identification information of the communication packet received, the first identification-information converting unit 35 c converts the formation identification information of the communication destination of the communication packet received, from the formation identification information of the second formation into the formation identification information of the own formation, and outputs the formation identification information of the own formation to the second identification-information converting unit 36 c. When the second identification-information converting unit 36 c finds car identification information of the first car as the own car in the communication-destination identification information of the communication packet output from the first identification-information converting unit 35 c, the second identification-information converting unit 36 c converts the car identification information of the communication destination of the communication packet, from the car identification information of the first car into the car identification information of the own car, and transmits the communication packet to the in-vehicle communication path 32 c via the in-vehicle communication interface 37 c. The communication terminal 33 c receives the communication packet that includes the device identification information of the communication destination indicating the communication terminal 33 c itself from the in-vehicle communication path 32 c.

As an example, a case that the communication terminal 33 a installed in the first vehicle 30 a in the first formation transmits data to the communication terminal 33 d installed in the second vehicle 30 d in the second formation can be also explained in a similar manner. For example, when the communication terminal 33 a installed in the first vehicle 30 a in the first formation transmits data to the communication terminal 33 b installed in the second vehicle 30 b in the same formation, this corresponds to a case of not performing communications between formations. Therefore, this operation is identical to that of the first embodiment. The second identification-information converting units 36 a and 36 b convert vehicle identification information, and the first identification-information converting units 35 a and 35 b do not convert formation identification information.

In the present embodiment, the first communication relay device and the second communication relay device according to the third embodiment are integrated within each vehicle and are used as one communication relay device. Other configurations, operations, and effects of the third embodiment are identical to those of the third embodiment.

Fifth Embodiment

FIG. 15 is an arrangement diagram of communication relay devices for a train within a train according to a fifth embodiment of the present invention. In FIG. 15, the train includes two formations of a formation 38 and a formation 39, for example. The formation 38 is a first formation, and includes a vehicle 42 a and a vehicle 42 b, for example. The vehicle 42 a is a first vehicle (a first car) in the first formation, and the vehicle 42 b is a second vehicle (a second car) in the first formation. The formation 39 is a second formation, and includes a vehicle 42 c and a vehicle 42 d, for example. The vehicle 42 c is a first vehicle (the first car) in the second formation, and the vehicle 42 d is a second vehicle (the second car) in the second formation. The number of formations and the number of vehicles in each formation are examples, and these numbers are not limited thereto.

A second communication relay device 44 a, a communication terminal 46 a, and an in-vehicle communication path 45 a connecting the second communication relay device 44 a and the communication terminal 46 a are installed in the vehicle 42 a. Similarly, a second communication relay device 44 b, a communication terminal 46 b, and an in-vehicle communication path 45 b connecting the second communication relay device 44 b and the communication terminal 46 b are installed in the vehicle 42 b. A second communication relay device 44 c, a communication terminal 46 c, and an in-vehicle communication path 45 c connecting the second communication relay device 44 c and the communication terminal 46 c are installed in the vehicle 42 c. A second communication relay device 44 d, a communication terminal 46 d, and an in-vehicle communication path 45 d connecting the second communication relay device 44 d and the communication terminal 46 d are installed in the vehicle 42 d. In the formations, the second communication relay devices 44 a, 44 b, 44 c, and 44 d perform operations identical to that of the communication relay device according to the first embodiment. Therefore, each of these second communication relay devices has an identification-information converting unit that converts car identification information. The number of communication terminals installed in each vehicle is an example, and plural communication terminals can be connected as shown in FIG. 2.

A first communication relay device 43 a is further installed in the vehicle 42 a, and the first communication relay device 43 a is connected to the second communication relay devices 44 a and 44 b via an inter-vehicle communication path 41 a of the first formation. The inter-vehicle communication path 41 a is a communication path arranged between vehicles within the first formation. A first communication relay device 43 c is further installed in the vehicle 42 c, and the first communication relay device 43 c is connected to the second communication relay devices 44 c and 44 d via an inter-vehicle communication path 41 c of the second formation. The inter-vehicle communication path 41 c is a communication path arranged between vehicles within the second formation.

An inter-formation communication path 40 is a communication path connecting formations. The first communication relay devices 43 a and 43 c are connected to the inter-formation communication path 40, and can communicate with each other using the inter-formation communication path 40. The configurations such that at each of the first communication relay devices 43 a and 43 c and the second communication relay devices 44 a, 44 b, 44 c, and 44 d has a communication interface to a connected communication path is identical to that of the first to fourth embodiments.

This is explained in detail. Each of the first communication relay devices 43 a and 43 c includes an inter-formation communication interface, and can communicate with each other between the formations via the inter-formation communication path 40 using each inter-formation communication interface. The first communication relay device 43 a includes an inter-vehicle communication interface, and can communicate between vehicles via the inter-vehicle communication path 41 a using this inter-vehicle communication interface. Similarly, the first communication relay device 43 c includes an inter-vehicle communication interface, and can communicate between vehicles via the inter-vehicle communication path 41 c using this inter-vehicle communication interface. Each of the second communication relay devices 44 a and 44 b includes an inter-vehicle communication interface, and can communicate between vehicles via the inter-vehicle communication path 41 a using each inter-vehicle communication interface. Similarly, each of the second communication relay devices 44 c and 44 d includes an inter-vehicle communication interface, and can communicate between vehicles via the inter-vehicle communication path 41 c using each inter-vehicle communication interface. The second communication relay device 44 a includes an in-vehicle communication interface, and can communicate within the vehicle via the in-vehicle communication path 45 a using this in-vehicle communication interface. Each of the second communication relay devices 44 b, 44 c, and 44 d also includes an in-vehicle communication interface in a similar manner to that of the second communication relay device 44 a, and also operates in a similar manner to that of the second communication relay device 44 a, and therefore explanations thereof will be omitted.

In the present embodiment, a structure of a communication packet explained in the third embodiment, that is, the structure of the communication packet shown in FIG. 3, is used. Each of the first communication relay devices 43 a and 43 c has an identification-information converting unit that converts formation identification information. As explained above, each of the second communication relay devices 44 a, 44 b, 44 c, and 44 d includes an identification-information converting unit that converts car identification information. These are identical to the conversions of car identification information and conversions of formation identification information explained in the first to fourth embodiments, and therefore detailed explanations thereof will be omitted.

The first communication relay device 43 a receives a communication packet, which is to be communicated between formations, out of communication packets transmitted from the second communication relay device 44 a or 44 b to the inter-vehicle communication path 41 a (that is, a communication packet transmitted to the second formation). The first communication relay device 43 a converts formation identification information, and transmits this communication packet to the inter-formation communication path 40. The first communication relay device 43 a converts formation identification information of a communication packet to the first formation out of communication packets received from the inter-formation communication path 40, and transmits the communication packet to the inter-vehicle communication path 41 a. The first communication relay device 43 c receives a communication packet communicated between formations out of communication packets transmitted from the second communication relay device 44 c or 44 d to the inter-vehicle communication path 41 c (that is, a communication packet transmitted to the first formation). The first communication relay device 43 c converts formation identification information, and transmits this communication packet to the inter-formation communication path 40. The first communication relay device 43 c converts formation identification information of a communication packet to the second formation out of communication packets received from the inter-formation communication path 40, and transmits the communication packet to the inter-vehicle communication path 41 c. The first communication relay devices 43 a and 43 c convert identification information of a communication packet between the formations by using the method explained in the second embodiment.

As an example, a case that the communication terminal 46 a installed in the first vehicle 42 a in the first formation transmits data to the communication terminal 46 c installed in the first vehicle 42 c in the second formation is explained. Communication-destination identification information of a communication packet transmitted from the communication terminal 46 a includes formation identification information of the second formation as formation identification information of a communication destination, car identification information of the first car as car identification information of the communication destination, and device identification information of the communication terminal 46 c as device identification information of the communication destination. Communication-source identification information of a communication packet transmitted from the communication terminal 46 a includes formation identification information of the own formation as formation identification information of a communication source, car identification information of the own car as car identification information of the communication source, and device identification information of the communication terminal 46 a as device identification information of the communication source. A communication packet transmitted from the communication terminal 46 a passes through the in-vehicle communication path 45 a, and is received by the second communication relay device 44 a via the in-vehicle communication interface. When the second communication relay device 44 a finds formation identification information other than the own formation or finds car identification information other than the own car in the communication-destination identification information of the communication packet received, the second communication relay device 44 a converts the car identification information of the communication source of the communication packet received, from the car identification information of the own car into the car identification information of the first car, using the identification-information converting unit, and transmits the communication packet to the inter-vehicle communication path 41 a via the inter-vehicle communication interface. The first communication relay device 43 a receives the communication packet from the inter-vehicle communication path 41 a. When the first communication relay device 43 a finds formation identification information other than the own formation in the communication-destination identification information of the communication packet received, the first communication relay device 43 a converts the formation identification information of the communication source of the communication packet received, from the formation identification information of the own formation into the formation identification information of the first formation, using the identification-information converting unit, and transmits the communication packet to the inter-formation communication path 40 via the inter-formation communication interface. The first communication relay device 43 c in the first vehicle 42 c in the second formation receives the communication packet from the inter-formation communication path 40 via the inter-formation communication interface. When the first communication relay device 43 c finds identification information of the second formation as the own formation in the communication-destination identification information of the communication packet received, the first communication relay device 43 c converts the formation identification information of the communication destination of the communication packet received, from the formation identification information of the second formation into the formation identification information of the own formation, using the identification converting unit, and transmits the communication packet to the inter-vehicle communication path 41 c via the inter-vehicle communication interface. The second communication relay device 44 c in the vehicle 42 c receives the communication packet via the inter-vehicle communication interface. When the second communication relay device 44 c finds car identification information of the first car as the own car in the communication-destination identification information of the communication packet received, the second communication relay device 44 c converts the car identification information of the communication destination of the communication packet received, from the car identification information of the first car into the car identification information of the own car, using the identification converting unit, and transmits the communication packet to the in-vehicle communication path 45 c via the in-vehicle communication interface. The communication terminal 46 c receives the communication packet that includes the device identification information of the communication destination indicating the communication terminal 46 c itself from the in-vehicle communication path 45 c.

Other operations of the fifth embodiment are identical to those of the first to fourth embodiments, and the present embodiment can achieve effects identical to those of the third and fourth embodiments.

Sixth Embodiment

FIG. 16 is an arrangement diagram of a communication relay device for a train within a train according to a sixth embodiment of the present invention. In FIG. 16, a communication relay device 49 is installed within a vehicle 47, and the communication relay device 49 is connected to communication terminals 51 a and 51 b, for example, via an in-vehicle communication path 50. The communication relay device 49 is also connected to an inter-vehicle communication path 48. The arrangement of the communication relay device 49 within the train is identical to that of the communication relay device in FIG. 7 or FIG. 14. The vehicle 47 is set as a first car of a first formation, for example.

The communication relay device 49 includes an inter-vehicle communication interface 52, a first identification-information converting unit 53, a second identification-information converting unit 54, a format-information storage unit 55, a format determining unit 56, and an in-vehicle communication interface 57. Functions of the inter-vehicle communication interface 52 and the in-vehicle communication interface 57 are identical to those of the first and second embodiments.

The first identification-information converting unit 53 has an identification-information conversion function of converting formation identification information. An operation of the first identification-information converting unit 53 is identical to those of the first identification-information converting units 35 a, 35 b, 35 c, and 35 d according to the fourth embodiment.

FIG. 17 depicts a structure of a communication packet transmitted and received by communication terminals of the present embodiment. As shown in FIG. 17, the communication packet includes communication-destination identification information, communication-source identification information, and a data portion. The communication-destination identification information includes formation identification information corresponding to a formation number of a communication destination, car identification information corresponding to a car number of the communication destination, and device identification information identifying a communication terminal within a vehicle of the communication destination. The communication-source identification information includes formation identification information corresponding to a formation number of a communication source, car identification information corresponding to a car number of the communication source, and device identification information identifying a communication terminal within a vehicle of the communication source.

In the third or fourth embodiment, specific car identification information indicating own vehicle is used as car identification information of a communication source. In the present embodiment, specific car identification information indicating own vehicle or a car number of a communication source is used as car identification information of the communication source.

For example, at the time of data transmission, when the communication terminal 51 a uses specific car identification information indicating own vehicle for car identification information of a communication source, a structure of a communication packet transmitted from the communication terminal 51 a is as shown in FIG. 18. As shown in FIG. 18, specific car identification information indicating own vehicle (identification information indicating own vehicle) is stored in car identification information of communication-source identification information, and device identification information indicating the communication terminal 51 a (device identification information of the communication terminal 51 a) is stored in device identification information of communication-source identification information. For identification information indicating own vehicle, for example, 0 (zero) can be used as a value of car identification information of the own car in a similar manner to that of the first embodiment.

When the communication terminal 51 b uses information indicating a car number for car identification information of a communication source, a structure of a communication packet transmitted from the communication terminal 51 b is as shown in FIG. 19. As shown in FIG. 19, car identification information indicating the first car (identification information indicating the first car) is stored in car identification information of communication-source identification information, and device identification information indicating the communication terminal 51 b (device identification information of the communication terminal 51 b) is stored in device identification information of communication-source identification information. For car identification information indicating the first car, a car number (“1”, in this case) can be used, for example.

As explained above, in the communication terminals 51 a and 51 b, a format of car identification information used for a vehicle installed with each communication terminal is set in advance. Each communication terminal uses identification information indicating own vehicle or uses a car number, for car identification information of a vehicle in which the communication terminal itself is installed.

The format-information storage unit 55 stores format information about whether to use identification information indicating own vehicle or to use a car number, for car identification information of the communication terminals 51 a and 51 b connected to the in-vehicle communication path 50. That is, communication format information for each communication terminal installed within a vehicle is stored in the format-information storage unit 55. The format determining unit 56 determines a communication terminal that transmits or receives a communication packet from device identification information of a communication packet, based on format information of each communication terminal stored in the format-information storage unit 55. The format determining unit 56 determines whether to use “identification information indicating own vehicle” or to use “car number” in car identification of a car in which the communication terminal is installed.

For example, there is considered a case that the communication terminal 51 a transmits a communication packet to the communication terminal 51 b. FIG. 20 is an example of a communication packet in this case. In the present embodiment, the communication terminal 51 a uses “identification information indicating own vehicle” for a format, and the communication terminal 51 b uses “car number” for a format. In FIG. 20, “identification information indicating own vehicle” is used as car identification information of communication-destination identification information. The communication relay device 49 receives the communication packet using the in-vehicle communication interface 57, and determines whether it is necessary to change a format of the communication packet destined to the communication terminal 51 b using the format determining unit 56 based on format information stored in the format-information storage unit 55. As a result, the communication relay device 49 sets “car number”, that is, a car number of the first car, as the car identification information of the communication-destination identification information, and transmits this communication packet from the in-vehicle communication interface 57 to the in-vehicle communication path 50. FIG. 21 depicts a structure of the communication packet in this case.

There is considered a case that when the communication terminal 51 a transmits a communication packet, which is as shown in FIG. 21, to the communication terminal 51 b. In this case, the communication relay device 49 receives the communication packet using the in-vehicle communication interface 57, and determines whether it is necessary to change a format of the communication packet destined to the communication terminal 51 b using the format determining unit 56 based on format information stored in the format-information storage unit 55. As a result, the communication relay device 49 determines that it is not necessary to change the format, and does not change the format. The communication terminal 51 b receives the communication packet, of which format is not changed, transmitted from the communication terminal 51 a.

Further, there is considered a case that the communication terminal 51 b transmits a communication packet to the communication terminal 51 a. FIG. 22 is an example of a communication packet in this case. In FIG. 22, “identification information indicating the first car” is used as the car identification information of communication-destination identification information. In this case, the communication relay device 49 receives the communication packet using the in-vehicle communication interface 57, and determines whether it is necessary to change a format of the communication packet destined to the communication terminal 51 a using the format determining unit 56 based on format information stored in the format-information storage unit 55. As a result, the communication relay device 49 sets “identification information indicating own vehicle” as the car identification information of the communication-destination identification information, and transmits this communication packet from the in-vehicle communication interface 57 to the in-vehicle communication path 50. FIG. 23 depicts a structure of the communication packet in this case.

Furthermore, there is considered a case that when the communication terminal 51 b transmits a communication packet, which is as shown in FIG. 23, to the communication terminal 51 a. In this case, the communication relay device 49 receives the communication packet using the in-vehicle communication interface 57, and determines whether it is necessary to change a format of the communication packet destined to the communication terminal 51 a using the format determining unit 56 based on format information stored in the format-information storage unit 55. As a result, the communication relay device 49 determines that it is not necessary to change the format, and does not change the format. The communication terminal 51 a receives a communication packet, of which format is not changed, transmitted from the communication terminal 51 b.

While the above operation is explained for communication terminals within the same vehicle, a similar conversion of identification information is performed when communication relay devices within a formation communicate with each other.

While an example of mutually using “information indicating own vehicle” and “car number” is explained for vehicle identification information of a communication terminal according to the present embodiment, “information indicating own formation” and “formation number” can be mutually used for formation identification information in a similar manner.

INDUSTRIAL APPLICABILITY

As described above, the communication relay device for a train according to the present invention is useful for communications between vehicles and formations of a train. 

The invention claimed is:
 1. A communication relay device for a train, mounted on a vehicle of a train having a vehicle formation including a plurality of vehicles, connected to an inter-vehicle communication path and to an in-vehicle communication path, and capable of relaying communications between communication terminals installed within own vehicle and communications between communication terminals installed in different vehicles, the communication relay device comprising: an inter-vehicle communication interface capable of transmitting and receiving a communication packet via the inter-vehicle communication path; an in-vehicle communication interface capable of transmitting and receiving a communication packet via the in-vehicle communication path; and an identification-information converting unit that converts, when vehicle identification information of a communication destination included in communication-destination identification information of a communication packet received from the in-vehicle communication path via the in-vehicle communication interface indicates other vehicle, vehicle identification information of a communication source, which is included in communication-source identification information of the communication packet and is vehicle identification information indicating own vehicle and used in common by each vehicle within the vehicle formation, into vehicle identification information for identifying a position of own vehicle within the vehicle formation, and then transmits the communication packet to the inter-vehicle communication path via the inter-vehicle communication interface, and converts, when vehicle identification information of a communication destination included in communication-destination identification information of a communication packet received from the inter-vehicle communication path via the inter-vehicle communication interface indicates own vehicle, the vehicle identification information of the communication destination into vehicle identification information indicating own vehicle and used in common by each vehicle within the vehicle formation and then transmits the communication packet to the in-vehicle communication path via the in-vehicle communication interface.
 2. The communication relay device for a train according to claim 1, further comprising: a format-information storage unit that has stored therein, for each communication terminal installed within own vehicle, information about whether a format of vehicle identification information used for own vehicle is a first format using vehicle identification information indicating own vehicle and used in common by each vehicle within the vehicle formation, or is a second format using vehicle identification information for identifying a position of own vehicle within the vehicle formation; and a format determining unit that determines whether it is necessary to change a format of the communication packet, based on the format information stored in the format-information storage unit, wherein the identification-information converting unit sets, when the vehicle identification information of the communication destination included in the communication-destination identification information of the communication packet received from the in-vehicle communication path via the in-vehicle communication interface indicates other vehicle and the format determining unit determines that format information used by a transmission-source communication terminal of the communication packet is the first format, the vehicle identification information for identifying a position of own vehicle within the vehicle formation as the vehicle identification information of the communication source included in the communication-source identification information of the communication packet and then transmits the communication packet to the inter-vehicle communication path via the inter-vehicle communication interface, and sets, when the vehicle identification information of the communication destination included in the communication-destination identification information of the communication packet received from the inter-vehicle communication path via the inter-vehicle communication interface indicates own vehicle and the format determining unit determines that format information used by a transmission-destination communication terminal of the communication packet is the first format, the vehicle identification information indicating own vehicle and used in common by each vehicle within the vehicle formation as the vehicle identification information of the communication destination and then transmits the communication packet to the in-vehicle communication path via the in-vehicle communication interface.
 3. A communication relay device for a train, mounted on a vehicle of a train having a plurality of vehicle formations, connected to an inter-vehicle communication path and to an in-vehicle communication path, and capable of relaying communications between communication terminals installed within own vehicle and communications between communication terminals installed in different vehicles, the communication relay device comprising: an inter-vehicle communication interface capable of transmitting and receiving a communication packet via the inter-vehicle communication path; an in-vehicle communication interface capable of transmitting and receiving a communication packet via the in-vehicle communication path; and an identification-information converting unit that converts, when vehicle-formation identification information of a communication destination included in communication-destination identification information of a communication packet received from the in-vehicle communication path via the in-vehicle communication interface indicates other vehicle formation, vehicle-formation identification information of a communication source, which is included in communication-source identification information of the communication packet and is vehicle-formation identification information indicating own vehicle formation and used in common by each vehicle formation within the train, into vehicle-formation identification information for identifying a position of own vehicle formation within the train, and then transmits the communication packet to the inter-vehicle communication path via the inter-vehicle communication interface, and converts, when vehicle-formation identification information of a communication destination included in communication-destination identification information of a communication packet received from the inter-vehicle communication path via the inter-vehicle communication interface indicates own vehicle formation, the vehicle-formation identification information of the communication destination into vehicle-formation identification information indicating own vehicle formation and used in common by each vehicle formation within the train and then transmits the communication packet to the in-vehicle communication path via the in-vehicle communication interface.
 4. A communication relay device for a train, mounted on a vehicle of a train configured by combining a plurality of vehicle formations each formation having one or more vehicles, connected to an inter-vehicle communication path and to an in-vehicle communication path, and capable of relaying communications between communication terminals installed within own vehicle and communications between communication terminals installed in different vehicles, the communication relay device comprising: an inter-vehicle communication interface capable of transmitting and receiving a communication packet via the inter-vehicle communication path; an in-vehicle communication interface capable of transmitting and receiving a communication packet via the in-vehicle communication path; a first identification-information converting unit that converts, when vehicle-formation identification information of a communication destination included in communication-destination identification information of a communication packet received via the in-vehicle communication interface indicates other vehicle formation, vehicle-formation identification information of a communication source, which is included in communication-source identification information of the communication packet and is vehicle-formation identification information indicating own vehicle formation and used in common by each vehicle formation within the train, into vehicle-formation identification information for identifying a position of own vehicle formation within the train before the communication packet is transmitted via the inter-vehicle communication interface, and converts, when vehicle-formation identification information of a communication destination included in communication-destination identification information of a communication packet received via the inter-vehicle communication interface indicates own vehicle formation, the vehicle-formation identification information of the communication destination into vehicle-formation identification information indicating own vehicle formation and used in common by each vehicle formation within the train before the communication packet is transmitted via the in-vehicle communication interface; and a second identification-information converting unit that converts, when vehicle identification information of a communication destination included in communication-destination identification information of a communication packet received via the in-vehicle communication interface indicates other vehicle or when vehicle-formation identification information of the communication destination indicates other vehicle formation, vehicle identification information of a communication source included in communication-source identification information of the communication packet into vehicle identification information for identifying a position of own vehicle within the vehicle formation before the communication packet is transmitted via the inter-vehicle communication interface, and converts, when vehicle identification information of a communication destination included in communication-destination identification information of a communication packet received via the inter-vehicle communication interface indicates own vehicle, the vehicle identification information of the communication destination into vehicle identification information indicating own vehicle and used in common by each vehicle within the vehicle formation before the communication packet is transmitted via the in-vehicle communication interface.
 5. The communication relay device for a train according to claim 4, further comprising: a format-information storage unit that has stored therein, for each communication terminal installed within own vehicle, information about whether a format of vehicle identification information used for own vehicle is a first format using vehicle identification information indicating own vehicle and used in common by each vehicle within the vehicle formation, or is a second format using vehicle identification information for identifying a position of own vehicle within the vehicle formation; and a format determining unit that determines whether it is necessary to change a format of the communication packet, based on the format information stored in the format-information storage unit, wherein the second identification-information converting unit sets, when the vehicle identification information of the communication destination included in the communication-destination identification information of the communication packet received via the in-vehicle communication interface indicates other vehicle or when the vehicle-formation identification information of the communication destination indicates other vehicle formation, and also when the format determining unit determines that format information used by a transmission-source communication terminal of the communication packet is the first format, the vehicle identification information for identifying a position of own vehicle within the vehicle formation as vehicle identification information of the communication source included in the communication-source identification information of the communication packet before the communication packet is transmitted via the inter-vehicle communication interface, and sets, when the vehicle identification information of the communication destination included in the communication-destination identification information of the communication packet received via the inter-vehicle communication interface indicates own vehicle and the format determining unit determines that format information used by a transmission-destination communication terminal of the communication packet is the first format, the vehicle identification information indicating own vehicle and used in common by each vehicle within the vehicle formation as the vehicle identification information of the communication destination before the communication packet is transmitted via the in-vehicle communication interface.
 6. A communication relay method for a train, for a communication relay device for a train, mounted on a vehicle of a train having a vehicle formation including a plurality of vehicles, connected to an inter-vehicle communication path and to an in-vehicle communication path, and capable of relaying communications between communication terminals installed within own vehicle and communications between communication terminals installed in different vehicles, the method comprising: converting, when vehicle identification information of a communication destination included in communication-destination identification information of a communication packet received from the in-vehicle communication path via an in-vehicle communication interface indicates other vehicle, vehicle identification information of a communication source, which is included in communication-source identification information of the communication packet and is vehicle identification information indicating own vehicle and used in common by each vehicle within the vehicle formation, into vehicle identification information for identifying a position of own vehicle within the vehicle formation and then transmitting the communication packet to the inter-vehicle communication path via an inter-vehicle communication interface; and converting, when vehicle identification information of a communication destination included in communication-destination identification information of a communication packet received from the inter-vehicle communication path via the inter-vehicle communication interface indicates own vehicle, vehicle identification information of the communication destination, which is vehicle identification information for identifying a position of own vehicle within the vehicle formation, into vehicle identification information indicating own vehicle and used in common by each vehicle within the vehicle formation and then transmitting the communication packet to the in-vehicle communication path via the in-vehicle communication interface.
 7. A communication relay method for a train, for a communication relay device for a train, mounted on a vehicle of a train including a plurality of vehicle formations, connected to an inter-vehicle communication path and to an in-vehicle communication path, and capable of relaying communications between communication terminals installed within own vehicle and communications between communication terminals installed in different vehicles, the method comprising: converting, when vehicle-formation identification information of a communication destination included in communication-destination identification information of a communication packet received from the in-vehicle communication path via an in-vehicle communication interface indicates other vehicle formation, vehicle-formation identification information of a communication source, which is included in communication-source identification information of the communication packet and is vehicle-formation identification information indicating own vehicle formation and used in common by each vehicle formation within the train, into vehicle-formation identification information for identifying a position of own vehicle formation within the train and then transmitting the communication packet to the inter-vehicle communication path via an inter-vehicle communication interface; and converting, when vehicle-formation identification information of a communication destination included in communication-destination identification information of a communication packet received from the inter-vehicle communication path via the inter-vehicle communication interface indicates own vehicle formation, vehicle-formation identification information of the communication destination into vehicle-formation identification information indicating own vehicle formation and used in common by each vehicle formation within the train and then transmitting the communication packet to the in-vehicle communication path via the in-vehicle communication interface.
 8. A communication relay method for a train, for a communication relay device for a train, mounted on a vehicle of a train configured by combining a plurality of vehicle formations each formation having one or more vehicles, connected to an inter-vehicle communication path and to an in-vehicle communication path, and capable of relaying communications between communication terminals installed within own vehicle and communications between communication terminals installed in different vehicles, the method comprising: converting, when vehicle identification information of a communication destination included in communication-destination identification information of a communication packet received from the in-vehicle communication path via an in-vehicle communication interface indicates other vehicle or when vehicle-formation identification information of a communication destination indicates other vehicle formation, vehicle identification information of a communication source included in communication-source identification information of the communication packet, which is vehicle identification information indicating own vehicle and used in common by each vehicle within the train, into vehicle identification information for identifying a position of own vehicle within the vehicle formation; converting, when vehicle-formation identification information of the communication destination indicates other vehicle formation, vehicle-formation identification information of a communication source included in communication-source identification information of the communication packet, which is vehicle-formation identification information indicating own vehicle formation and used in common by each vehicle formation within the train, into vehicle-formation identification information for identifying a position of own vehicle formation within the train and then transmitting the communication packet to the inter-vehicle communication path via an inter-vehicle communication interface; converting, when vehicle-formation identification information of a communication destination included in communication-destination identification information of a communication packet received from the inter-vehicle communication path via the inter-vehicle communication interface indicates own vehicle formation, vehicle-formation identification information of the communication destination, which is vehicle-formation identification information for identifying a position of own vehicle formation within the train, into vehicle-formation identification information indicating own vehicle formation and used in common by each vehicle formation within the train; and converting vehicle identification information of the communication destination, which is vehicle identification information for identifying a position of own vehicle within a vehicle formation, into vehicle identification information indicating own vehicle and used in common by each vehicle within the train and then transmitting the communication packet to the in-vehicle communication path via the in-vehicle communication interface. 